Anchor for anchoring electrode leads used in cochlear implantation

ABSTRACT

A method for implanting electrodes in or around a human cochlea that involves inserting one end of an anchor in the temperal bone, and functionally engaging a lead to the electrode with the anchor. Numerous anchor embodiments are described together with tools for inserting some of the anchors.

TECHNICAL FIELD

The present invention relates to methods and devices used in implantingelectrodes in or around the human cochlea.

BACKGROUND ART

Several methods have been developed to electrically stimulate nervefibers in the cochlea of a deaf person in a pattern roughlycorresponding to longitudinal mechanical waves produced in theenvironment (which waves are heard as sound by persons with normalhearing) to thus produce the sensation of sound in the deaf person. Thedetails and results of one such method are set forth in a documententitled "Cochlear Implants: Progress and Perspectives" edited byWilliam F. House and Karen I. Berliner, and which is Supplement91-Volume 91, Mar.-Apr. 1982, No. 2, Part 3 of the Annals of Otology,Rhinology and Laryngology, published by The Annals Publishing Company,4949 Forest Park Boulevard, St. Louis, Mo. 63108, copyright 1982, thecontent whereof is hereby incorporated herein by reference.

Generally such methods involve implanting an internal electromagneticcoil connected by leads to active and ground electrodes under the skincovering the person's skull and positioning the electrodes atpredetermined locations in or adjacent the cochlea. An externally wornadjustable transducer is then used to produce electrical signals inresponse to longitudinal mechanical waves produced in the environmentand received via a microphone on the device, and to couple thoseelectrical signals to an external electromagnetic coil positioned on theoutside of the skin opposite the coil under the skin. Electrical signalscorresponding to those produced by the transducer are produced in theinternal coil by magnetic coupling between the coils, and those signalsstimulate the cochlea via the electrodes. While the signals do notproduce the same sound sensations from the mechanical waves that thewaves produce via the normal human ear, they do produce a range of soundsensations that, with training, can be used by the person to helpidentify the source of the waves and in many cases to help the personunderstand human speech.

Implanting the coil with its leads and electrodes under the skincovering the person's head generally comprises (1) exposing the outersurface of the person's temporal bone behind the ear, which is typicallydone by cutting an arcuate slit in the skin, muscle, and other tissueoverlaying that bone, separating, and laying back the flap thusproduced; (2) making an opening in the temporal bone through the mastoidand facial recess portions of the temporal bone between the outersurface of the temporal bone and the round window in the cochlea; (3)forming a recess for the coil via a surgical drilling device in theexposed squamous portion of the temporal bone; (4) locating andattaching the internal coil in the recess; (5) positioning the groundelectrode in the eustachian tube or some other location such as theopening in the mastoid or under the temporalis muscle; (6) positioningthe lead terminating at the active electrode through the surgicallyprepared opening with the electrode at a predetermined position relativeto the cochlea (e.g., which position may be at the outside surface ofthe round window of the cochlea or inside the cochlea with the leadpassing through the round window); (7) anchoring the leads in placethrough the use of an acceptable adhesive or by packing tissues from thehead around them in the opening; and (8) then replacing the flap ofskin, muscle, and other tissues by suturing it in place over the coiland opening, and allowing the slit that formed the flap to heal.

Other similar methods have involved the use of a plurality of leadswhich terminate at spaced active electrodes adapted to be inserted intothe cochlea through the round window under the theory that selectiveactivation of the electrodes may selectively stimulate different nervesin the cochlea and result in better sound discrimination by the person.

The use of any such method has presented the problem of properlypositioning the electrodes with respect to the cochlea and holding theelectrodes in that desired position. Experience has shown thatpositioning of the active electrode has often disrupted the delicatesoft tissues of the cochlea (e.g., the basilar membrane or spiralligament), and that a positioned electrode is sometimes inadvertentlymoved from the desired position during the operation. Also, it issometimes necessary to replace the internal coil during a revisionsurgery which is done by again making an arcuate incision and foldingback a flap of skin, muscle, and other tissues from over the internalcoil, cutting the lead or leads connected to the internal coil,reconnecting a new internal coil, and suturing the flap in place overthe new internal coil. Inadvertent movement of the electrodes hasoccurred during such severing and reconnecting of the leads which canresult in damage to the cochlea or an improper new position for theelectrodes. Such movement occurs because the anchor tissues packedaround the leads do not attach firmly to the lead, and because of theslight force necessary to move the leads.

DISCLOSURE OF THE INVENTION

The present invention provides an effective method for positioning oneor more of electrodes while they are being implanted through asurgically prepared opening in the temporal bone as described above, andfor anchoring those electrodes in place to maintain their position bothduring the operation by which they are implanted and thereafter,including during changing of the internal coil should that occur.

According to the present invention there is provided an improvement inthe method of implanting one or more electrodes in or adjacent the humancochlea, which electrode affords electrical stimulation of nerve fibersto produce the sensation of sound by positioning a lead terminating atthe electrode through an opening surgically made in the temporal boneand with the electrode at a predetermined position relative to thecochlea (e.g., within the cochlea or closely adjacent to its roundwindow). The improved method includes (1) providing an anchor having afirst end portion, and having a second end portion adapted to engage aportion of the lead and restricts longitudinal, transverse androtational movement thereof relative to the anchor; (2) forming a socketfrom the opening into the temporal bone, which socket is adapted toreceive and hold the first end portion of the anchor; (3) inserting thefirst end portion of the anchor in the socket; and (4) engaging aportion of the lead with the second end portion of the anchor to therebyrestrict longitudinal, transverse and rotational movement of theelectrode.

It has been found that the method has particular advantages where thesteps of inserting the first end portion of the anchor in the socket andengaging a portion of the lead with the second end portion of the anchorare performed prior to final positioning of the electrode relative tothe cochlea, and where the positioning step includes the step of pullingthe lead (which typically has a diameter of about 0.035 inch or 0.09 cm)through the anchor against the frictional engagement of its second endportion to provide such final positioning. Such pulling of the lead(which may be done with a pliers-like instrument such as a forceps)facilitates accurate positioning of the electrode by aligning parts ofor indicating marks on the lead with respect to anatomical structures(such as the round window), thereby restricting damage to the delicatecochlear tissues by improper positioning of the electrode.

One anchor adapted to be inserted in the temporal bone and to be engagedwith one or more leads extending to an electrode to help position andretain the electrode at a desired location relative to the cochleacomprises: (1) a metal wire having a first end portion adapted to beinserted in a socket in the temporal bone and comprising means adaptedto firmly engage the walls defining the socket, and an oppositegenerally U-shaped end portion; and (2) a layer of resiliently elasticpolymeric material over the adjacent surfaces of the U-shaped endportion, the adjacent surfaces of the layer of polymeric material beingspaced to frictionally receive a portion of the lead therebetween, andthe layer being sufficiently thick to insure proper electricalinsulation between the wire and the lead.

Preferably the first end portion of the anchor includes a barbprojecting along one side and toward the second portion of the anchor,and the socket is sized so that its walls will resiliently deflect thebarb toward the rest of the first end portion when the first portion isinserted in the socket. The first end portion of the anchor ispreferably inserted in the socket when the anchor is rotated froa itsdesired orientation (e.g., by about 90 degrees), and the anchor is thenrotated to its desired orientation. This will cause the barb to move outof alignment with any groove it formed in the wall defining the socketas it was inserted to thereby enhance its holding power in the bone,which holding power is produced by pressure applied to the wallsdefining the socket by the resiliently deflected barb.

While the anchor described above is preferred because of its ease ofinsertion in the temporal bone and the ease with which the leads may beengaged with it, many other anchor forms described hereinafter also maybe found useful, such as bone screws with specially formed transverseslots in their heads.

Also, novel insertion tools have been found useful to facilitateinserting the various anchors in the temporal bone. Such tools are eachadapted to releasably engage one form of the anchor so that the anchorcan be inserted in the socket by manual manipulation of the tool withoutthe probability that the anchor will be prematurely disengaged from thetool and lost in the recesses of the head, and the tool is adapted to beeasily disengaged from the anchor after its insertion in the socket.

BRIEF DESCRIPTION OF DRAWING

The present invention will be further described with reference to theaccompanying drawing wherein like numbers refer to like parts in theseveral views and wherein:

FIGS. 1, 2 and 3 are fragmentary sectional views of the temporal boneand adjacent structures in a human skull illustrating certain steps usedto position an electrode included in a method according to the presentinvention;

FIGS. 4 and 5 are fragmentary side views, partially in section, of thehuman skull shown in FIGS. 1, 2 and 3 which also illustrates steps inthe method according to the present invention;

FIG. 6 is an enlarged side view of an anchor which is shown beinginserted or shown in place in FIGS. 2, 3, 4 and 5;

FIG. 7 is an enlarged sectional view of an insertion tool for use ininserting the anchor of FIG. 6 and which is shown being used in FIG. 2;

FIG. 8 is a side view of a first alternate embodiment of an anchor whichmay be used in the method according to the present invention;

FIG. 9 is an enlarged sectional view of a first alternate embodiment ofan installation tool for use with the anchor shown in FIG. 8;

FIG. 10 is a side view of a third alternate embodiment of an anchorwhich may be used in the method according to the present invention;

FIG. 11 is a side view of a fourth alternate embodiment of an anchorwhich may be used in the method according to the present invention;

FIG. 12 is a side view of a fifth alternate embodiment of an anchorwhich may be used in the method according to the present invention;

FIG. 13 is a side view of a sixth alternate embodiment of an anchorwhich may be used in the method according to the present invention;

FIG. 14 is a side view of a seventh alternate embodiment of an anchorwhich may be used in the method according to the present invention;

FIG. 15 is a side view of an eighth alternate embodiment of an anchorwhich may be used in the method according to the present invention; and

FIG. 16 is a side view of a ninth alternate embodiment of an anchorwhich may be used in the method according to the present invention.

DETAILED DESCRIPTION

Referring now to FIGS. 1 through 5 there are illustrated steps of animproved method according to the present invention for implanting anactive electrode 10 and a ground electrode 12 in or adjacent a humancochlea 14 (which electrodes 10 and 12 afford electrical stimulation ofnerve fibers to produce the sensation of sound), by positioning leads 15and 16 between an electromagnetic coil 17 and the electrodes 10 and 12through an opening 18 surgically made in a temporal bone 20 andpositioning the electrodes 10 and 12 at predetermined positions relativeto the cochlea 14 (e.g., such as with the active electrode 10 within thecoclea 14 and the ground electrode 12 within the eustachian tube 22 asillustrated, or alternately (not shown) with the active electrode 10 ata round window 24 of the cochlea 14). The improved method includes (1)providing an anchor 26 (FIG. 5) having a first end portion 28 and havingan opposite second end portion 30 adapted to frictionally engage aportion of one or both of the leads 15 and 16 and restrict longitudinal,transverse and rotational movement thereof relative to the anchor 26;(2) forming a socket 32 (as with a surgical drill 34 as is shown inFIG. 1) from the opening 18 into the temporal bone 20, which socket 32is adapted to frictionally receive the first end portion 28 of theanchor 26; (3) inserting the first end portion 28 of the anchor 26 inthe socket 32 (FIG. 4) which may be done through the use of an insertiontool 36 as is shown in FIG. 2 or otherwise; and (4) engaging a portionof one or both of the leads 15 and 16 with the second end portion 30 ofthe anchor (FIGS. 3 and 5).

Preferably the method is performed by inserting the first end portion 28of the anchor 26 in the socket 32, and engaging a portion of the lead 15or 16 with the second end portion 30 of the anchor 26 prior to finalpositioning of the electrode 10 or 12, and then positioning the lead 15or 16 with the electrode 10 or 12 at its final predetermined positionrelative to the cochlea 14, with the positioning step comprising thestep of pulling the lead 15 or 16 through the anchor 26 as with aforceps 38 against the frictional engagement of the second end portion30 of the anchor 26 with the lead 15 or 16 (FIG. 3) to achieve the finalpositioning of the electrode 10 or 12. It has been found that suchpulling of the lead 15 or 16 through the anchor facilitates accuratepositioning of the electrode 10 or 12 by aligning parts of or indicatingmarks on the leads 15 or 16 with respect to anatomical structures (suchas the round window 24), thereby restricting damage to the delicatetissues of the cochlea 14 by improper positioning of the electrode 10 or12.

As is best seen in FIG. 6, the anchor 26 adapted to be inserted in thetemporal bone 20 and to engage with one or both of the leads 15 or 16 tohelp position and retain the electrode 10 or 12 at a desired locationrelative to the cochlea 14 comprises: (1) a metal wire (e.g., ofcommercially pure titanium, 0.038 inch or 0.096 cm in diameter)providing the first end portion 28 adapted to be inserted in the socket32 in the temporal bone 20, and the opposite second end portion 30 whichis generally U-shaped; and (2) a resiliently elastic polymeric tube 40(e.g., medical-grade silastic tubing with a wall thickness of about0.017 inch or 0.043 cm) over the U-shaped second end portion 30 whichprovides a layer of the polymeric material over the adjacent surfaces ofthe wire along its U-shaped end portion 30, with the adjacent surfacesof the layer or tube 40 being spaced to frictionally receive a portionof the lead 15 or 16 therebetween. The layer or tube 40 thus serves bothto frictionally hold the lead 15 or 16 in place while affordinglongitudinal movement of the lead 15 or 16 under a force applied by theforceps 38, and also helps to electrically insulate the lead 15 for theactive electrode 10 from the metal wire part of the anchor 26.

The distal tip 42 of the second U-shaped end portion 30 preferablydiverges away from its proximal end to afford pressing or pulling thelead therebetween. The anchor 26 is adapted so that when its first endportion is engaged in the socket 32, the distal tip 42 can be spacedfrom the temporal bone 20 so that the space between the temporal bone 20and the distal tip 42 and the space between the adjacent surfaces of thetube 40 over the second end portion 30 provide, in combination, agenerally L-shaped space adapted to receive a portion of the lead 15 or16. This L-shaped space includes an outer portion between the temporalbone 20 and distal tip 42 which will help to initially locate the lead15 or 16 adjacent the anchor 26 and an inner portion between theadjacent walls of the tube 40 in which the lead 15 or 16 can befrictionally held.

Also, the first end portion 28, as illustrated, has a barb 44 whichprovides means adapted to firmly engage the walls defining the socket32. The barb 44 is formed by slotting the first end portion 28 at anacute angle to its axis (e.g., as with a 0.006 inch wide slot formed byelectro discharge machining) and bending the tip of the triangular partthus formed away from the rest of the first end portion 28 to providethe barb 44 which projects along one side of the first end portion 28and toward the second end portion 30 of the anchor 26. The barb 44projects sufficiently (e.g., 0.006 inch or 0.015 centimeters) that itcan be resiliently deflected toward the rest of the first end portion 28by the walls of the socket 32 in which it is inserted, and may be formedwith a rounded tip so that the anchor 26 can be pulled from the socket32 without the danger of breaking off the tip of the barb 44 or part ofthe first end portion 28.

The insertion tool 36 adapted to insert the anchor 26 is best seen inFIG. 7. As illustrated, the tool 36 comprises a mostly cylindrical blade46 having a central axis and one end portion that projects into and isfixed within a socket 48 in a handle 50 by a pin 51. A hollow tubularsleeve 52 is mounted for axial sliding movement along the blade 46 from(1) an outer engage position to which the sleeve 52 is biased by aspring 53 between the sleeve 52 and the handle 50 at the bottom of thesocket 48 (FIGS. 2 and 7); and (2) a release position (not shown) withthe sleeve 52 telescoped farther within the socket 48, which engage andrelease positions are defined by the engagement of the pin 51 atopposite ends of opposed axially extending slots 54 in the sleeve 52. Anend drive portion is provided at the end of the blade 46 opposite thehandle 50. The end drive portion has a planar axially extending sidesurface 56, a radially extending pressure surface 57, and a lug 58projecting from the side surface 56. The surfaces 56 and 57 and lug 58are sized and spaced so that either side surface of the anchor 26 may bepositioned against the side surface 56 of the blade 46 with the firstend portion 28 of the anchor 26 projecting axially away from the distalend of the blade 46, an end surface of the second end portion 30opposite the first end portion 28 abutting the pressure surface 57, andwith the lug 58 received in the transverse opening through the secondend portion 30 of the anchor 26 between the adjacent surfaces of thetube 40. In this position side or drive surfaces of the lug 58 alignedaxially of the blade 46 are in engagement with adjacent spaced sidesurfaces of the tube 40 of the anchor 26 and can transfer torque theretowhen the handle 50 is rotated about its axis. Also, a retaining surfaceof the lug 58 opposite the pressure surface 57 is adjacent a supportsurface of the anchor 26 on the side of the tube 40 opposite the endsurface of the second end portion 28 to retain the part of the anchorsecond end portion 28 therebetween. When the sleeve 52 is in its engageposition it will project over the lug 58 and partially along the secondend portion 30 of the anchor 26 so that the second end portion 30 of theanchor 26 will be retained on the tool 36 by the surfaces 56, 57, lug 58and inner surface of the sleeve 52 (FIG. 2). When the sleeve 52 is movedto its release position against the bias of the spring 53, however, itretracts from over the lug 58 so that the lug 58 can be withdrawn fromwithin the opening in the second end portion 30 of the anchor 26 torelease the insertion tool 36 from the anchor 26.

To use the insertion tool 36, the sleeve 52 is moved to its releaseposition, the anchor 26 is positioned along the side surface 56 with thelug 58 within its U-shaped second end portion 30, and the sleeve 52 isallowed to move to its engage position under the influence of the spring53. The tool 36 can then be used to press the projecting first endportion 28 of the anchor 26 into the socket 48, with force applied tothe tool 36 being transferred to the anchor 26 through the pressuresurface 57, and to rotate the anchor to a desired location (indicated bya position indicating notch 59 across the end of the handle 50) withrotational force being applied to the anchor 26 via the lug 58 and theside surface 56. After the anchor 26 is in place, the sleeve 52 canagain be moved to its release position and the lug 58 moved sidewaysfrom within the U-shaped second end portion 30 of the anchor 26 toremove the tool 36 from the inserted anchor 26.

FIG. 8 illustrates a first alternate embodiment of an anchor that couldbe used in the method according to the present invention, generallydesignated by the reference numeral 60. The anchor 60 is a screw-likemember, made by modifying a standard bone screw, which comprises athreaded first end portion 62 adapted to be inserted in a socket in atemporal bone; and a head 64 defining a second end portion of the anchor60. The head 64 has a transverse opening or slot 65, modified by cuttingvia electro-discharge machining, which slot includes an outer axiallyaligned portion 66 having an inlet opening 67 extending across the head64, and an inner portion 68 extending generally at a right angle to theouter portion 66. The outer slot portion 66 has arcuate walls and awidth adapted to receive a lead with light friction between the arcuatewalls and the lead to facilitate moving the lead to position it afterthe lead is engaged in the outer slot portion 66, whereas the inner slotportion 68 is sized to firmly frictionally engage the lead to hold it inplace. Thus an electrode at the end of the lead may be positioned whilethe lead is in the outer slot portion 66, and then pushed into the innerslot portion 68 to hold it in place. The head 64 may be coated with asuitable insulating material (such as a polymer) to help frictionallyhold the lead and to help electrically insulate the wire in the lead, ormay be entirely formed of polymeric material.

An insertion tool 70 adapted to insert the anchor 60 is best seen inFIG. 9. As illustrated, the tool 70 comprises a blade 72 having acentral axis and one end portion that projects into and is fixed withina socket in a handle 73 by a pin 74. A tubular sleeve 75 is mounted foraxial sliding movement along the blade 72 from (1) an outer engageposition to which the sleeve 75 is biased by a spring 76 around theblade 72 between an inwardly projecting lip 77 on the sleeve 75 and thehandle 73 with the lip 77 abutting an outwardly projecting flange 78 onthe blade 72; and (2) a release position with the sleeve 75 abutting thehandle 73. And end drive portion is provided at the end of the blade 72opposite the handle 73. The end drive portion has an end pressuresurface 79 adapted to engage the end surface on the head 64 of theanchor 60, and a generally L-shaped projecting drive lug 80 adapted toslide transversely into the opening of slot 65 in the head 64 with thethreaded end portion 62 of the anchor 60 projecting axially away fromthe pressure surface 79 of the blade 72. In this position side or drivesurfaces of the lug 80 aligned axially of the blade 72 are in engagementwith adjacent side surfaces defining the slot 65 in the head 64 of theanchor 60 and can transfer torque thereto as the handle 73 is rotatedabout its axis. Also, a retaining surface of the lug 80 opposite thepressure surface 79 is adjacent a support surface of the anchor 60 onthe side of the part of the head 64 opposite its end surface to retainthat part of the head 64 therebetween. When the sleeve 75 is in itsengage position it will project over the lug 80 and along the sides ofthe head 64 of the anchor 60 when it is positioned with the L-shaped lug80 in its slot 65 so that the anchor 60 will be retained on the tool 70via the lug 80 and the sleeve 75. When the sleeve 75 is moved to itsrelease position against the bias of the spring 76, however, it retractsfrom over the head 64 of the anchor 60 so that the lug 80 can be slidtransverse of the anchor 60 from within the head 64 of the anchor 60 torelease the insertion tool 70 from the anchor 60.

To use the insertion tool 70, the sleeve 75 is moved to its releaseposition, and the head 64 of the anchor 60 is slid transversely over thelug 80 with the lug 80 in the slot 65 until the head 64 is centered onthe surface 79. The sleeve 75 is then allowed to move to its engageposition under the influence of the spring 76. The tool 70 can then beused to rotate the projecting threaded first end portion 62 of theanchor 60 into a socket with the lug 80 acting as a screwdriver blade totransfer rotational force from the tool 70 to the anchor 60. After theanchor 60 is in place with the slot 65 properly aligned (which can bedetermined by the alignment of a position indicating notch 71 across theend of the handle 73), the sleeve 75 can be moved to its releaseposition and the lug 80 can be slid sideways from within the slot 65 inthe head 64 to release the tool 70 from the inserted anchor 60.

FIG. 10 illustrates a third alternate embodiment of an anchor 81according to the present invention, which, like the anchor 60, is ascrew-like member made by modifying a standard bone screw, and whichcomprises a threaded first end portion 82 adapted to be inserted in asocket in a temporal bone; and a head 84 defining a second end portionof the anchor 81. The head 84 has a transverse slot 85 made by cuttingvia an electron emission machine and which, like the slot 65 in theanchor 60, includes an outer axially parallel portion 86 having an inletopening 87 extending across the head 84, and an inner portion 88extending generally at a right angle to the outer portion 86, whichportions 86 and 88 provide essentially the same functions as the innerand outer portions 68 and 66 of the slot 65 in the anchor 60. Unlike theslot 65 in the anchor 60, however, the slot 85 is cut into the head 84from its surface adjacent the threaded end portion 82. The anchor 80thus must be inserted by standard screw driving equipment via aconventional screw-driver receiving slot 89.

FIG. 11 shows a fourth alternate embodiment of an anchor that can beused in the method according to the present invention generallydesignated by the reference numeral 100. The anchor 100 is particularlyadapted for use with leads that benefit from support adjacent both endsof an opening formed in a temporal bone between its surface and theround window of a cochlea, as the anchor 100 is adapted to engage thelead at two spaced positions. The anchor comprises a metal wire 102having a first end portion 103 formed with a barb 104 and adapted to beinserted in a socket in a temporal bone, and a second end portion 105adapted to engage portions of a lead. The second end portion 104comprises first and second spaced generally inverted U-shaped parts 106positioned with the major planes of the U-shaped parts 106 generallyparallel, and a connecting part 107 connecting ends of the U-shapedparts 106 that extends generally at right angles to the planes of theU-shaped parts 106. The first end portion 103 projects from the end ofone of the U-shaped parts 106 opposite the connecting part 107.Resiliently elastic polymeric tubes 108 are positioned over the wire 102around the U-shaped parts 106, with the adjacent surfaces of the tubes108 spaced to frictionally receive portions of a lead therebetween.

FIG. 12 shows a fifth alternate embodiment of an anchor according to thepresent invention generally designated by the reference numeral 110. Theanchor 110, like the anchor 100, is also particularly adapted for usewith leads that benefit from support adjacent both ends of an openingformed in a temporal bone between its outer surface and the round windowor oval window of a cochlea, as the anchor 110 is adapted to also engagethe leads at two spaced positions. The anchor 110 comprises a metal wire111 having a first end portion 112 formed with a barb 113 and adapted tobe inserted in a socket in a temporal bone, and a second end portion 114adapted to engage portions of two leads. The second end portion 114comprises first and second spaced parts 115 which are 5 generally in theshape of two adjacent U's or W-shaped and are positioned with the majorplanes of the W-shaped parts 115 generally parallel, and a connectingpart 116 connecting ends of the W-shaped parts 115 that extendsgenerally at right angles to the planes of the W-shaped parts 115. Thefirst end portion 112 projects from the end of one of the W-shaped parts115 opposite the connection part 116. Resiliently elastic polymerictubes 117 are positioned over the wire 112 around the W-shaped parts115, with the adjacent surfaces of the tubes 117 spaced to frictionallyreceive portions of the leads therebetween.

FIG. 13 illustrates a sixth alternate embodiment of an anchor 120 whichmay be used in the method according to the present invention. The anchor120 is a generally U-shaped member of metal or a suitable polymericmaterial comprising two leg portions 121 and 122 joined at an apex 123,which anchor 120 is resiliently bendable at the apex 123. The U-shapedmember has transverse notches 124 along opposing surfaces of the legportions 121 and 122 adapted to receive and retain a lead therebetween.The anchor 120 may be inserted apex 123 first into a socket in atemporal bone so that the walls of the socket press the leg portions 121and 122 together and against a lead in the notches 124 to frictionallyretain the lead therebetween. The distal end 125 of the leg 121 isenlarged and adapted to receive force to drive the anchor 120 into asocket.

FIG. 14 illustrates yet a seventh alternate embodiment of an anchor 130which may be used in the method according to the present invention. Theanchor 130 comprises a conventional bone screw 131 which may be engagedin a socket in a temporal bone, and a wire having at one end a loop 132adapted to be engaged under a head 133 of the screw 131 engaged in thesocket, and a generally U-shaped portion 134 over which a resilientlyelastic tube 135 is positioned so that a lead may be frictionallyretained between the adjacent surfaces of the tube 135. Alternately nosleeve need be used, and the U-shaped end portion could be shaped toreceive a collar over a lead like a collar 147 of an anchor 140 (FIG.15).

FIG. 15 shows an eighth alternate embodiment of an anchor which may beused in the method according to the present invention generallydesignated by the reference numeral 140. The anchor 140 comprises (1) ametal wire 141 having a first end portion 142 formed with a barb 143 andadapted to be inserted in a socket in a temporal bone, and a second endportion 145 which is generally U-shaped, and (2) the resiliently elastichollow cylindrical polymeric collar 147 adapted to be slid lengthwiseover a lead with the lead in its central opening and then to be pressedinto and compressed within the U-shaped second portion 145 so that thecollar 147 provides a layer of resiliently elastic polymeric materialover the adjacent surfaces of the wire 141 along the U-shaped endportion 145 and has adjacent surfaces spaced to receive and frictionallyengage the lead therebetween to secure the lead to the anchor 140.

FIG. 16 shows a ninth alternate embodiment of an anchor which may beused in the method according to the present invention generallydesignated by the reference numeral 150. The anchor 150 comprises (1) ametal wire 151 having a first end portion 152 formed with a barb 153 andadapted to be inserted in a socket in a temporal bone, and a second endportion 155 which is formed into a generally U-shaped loop, and (2) aresiliently elastic hollow cylindrical polymeric plug 157. The plug 157has a generally cylindrical portion with a flange 158 at one end, andhas an axially extending slot 159 opening through one side surfaceadapted to receive a lead. After the lead is positioned within the slot159, the cylindrical portion can be pressed into the second end portion155 of the anchor 150 which will compress the cylindrical portion of theplug 157 so that the plug 157 provides a layer of resiliently elasticpolymeric material over the adjacent surfaces of the wire along theU-shaped end portion 155, and has adjacent surfaces spaced to receiveand frictionally engage the lead therebetween to secure it to the wire151.

We have now described the method according to the present invention andnumerous embodiments of anchors that may be used in that method. It isapparent that other embodiments of the anchor could be used in themethod such as may result by interchanging or slightly modifying partsof the various anchors described, without departing from the spirit ofthe present invention. Thus the scope of the present invention shouldnot be limited by the description herein, but only by the method stepsand structures recited in the dependent claims and their equivalents.

As an example concerning the anchor 26 shown in FIG. 6 and the methodillustrated in FIGS. 1 through 5, some surgeons may prefer to use theside of the anchor 26 between the distal tip 42 and the temporal bone 20with which it is engaged as a guide during positioning of a lead andelectrode, and to then pull the lead between the adjacent surfaces ofthe tube 40 over the U-shaped end portion 30 of the anchor 26.

We claim:
 1. In combination, an electrical lead extending to anelectrode and an anchor adapted to be inserted in the temporal bone of ahuman skull and engaging with said lead to help position and hold theelectrode at a desired location relative to a cochlea in said skull,said anchor being a screw-like member with a central axis comprising athreaded first end portion adapted to be inserted in a socket in thetemporal bone; and a head defining a second end portion of said anchor,said head having a slot transverse to said axis, said slot beinggenerally L-shaped and extending entirely across said head and having aninlet opening extending entirely across said head, said generallyL-shaped slot having an outer portion extending inwardly of said headfrom said inlet opening, and an inner portion extending from the end ofsaid outer portion opposite said inlet opening generally at a rightangle to said outer portion, said outer portion having a width adaptedto freely receive a portion of said lead and said inner portionfrictionally receiving the portion of said lead.
 2. An anchor accordingto claim 1 wherein said outer portion of said slot opens through thesurface of said head opposite said first end portion.
 3. An anchoraccording to claim 1 wherein said outer portion of said slot opensthrough the surface of said head adjacent said first end portion.